The present invention relates to refractory compositions capable, when mixed with water or other fluid, of forming hydraulic-setting castable and gunning refractories for lining various vessels and transfer lines used in the processing of materials, the compositions having high abrasion resistance and a relatively low thermal conductivity.
While a large number of castable and gunning compositions per se are old and well known, there are many special attributes required depending on the conditions of use which often renders those presently available not entirely suitable.
Thus, for example, castable refractories used in the petrochemical industry for lining transfer lines employed in fluid catalytic cracking and fluid coking units are not entirely satisfactory due to their high thermal conductivity. Efforts to reduce the termal conductivity by addition of lightweight aggregates such as perlite, vermiculite and the like have not been satisfactory since the strength of the resultant cast or gunned refractory is greatly reduced.
The present castables are also not entirely satisfactory since in such lines the catalysts; which are aluminum based, and the coke are highly abrasive and travel at elevated speeds creating significant erosion problems throughout the entire system. Gunning mixes used for such purposes also lack the necessary low thermal conductivity, abrasion resistance, and desired strength.
U.S. Pat. No. 4,656,146 discloses an improved abrasion-resistant refractory composition for petrochemical applications and it does overcome the prior art problem of having a low thermal conductivity with an acceptable density. However, while generally satisfactory, such castable still does not have the degree of abrasion resistance combined with low thermal conductivity that is desired.